The present invention relates to a projection type display apparatus which projects a video or image on a projection surface with use of image display elements such as liquid crystal display elements, to a light source device which has a plurality of light source units and which condenses light fluxes from the plurality of light source units into a single light flux and then projects the condensed light flux onto an illumination optical system provided in a subsequent stage, and also to a technique for providing a highly-efficient projection type display apparatus without increasing the size of the light source.
In a projection type display apparatus for displaying, in an enlarged manner, an image plane of reflection or transmissive liquid crystal panel or a display screen, created by an image display element made of a plurality of very small or micro mirrors arranged thereon, on a screen, a board or the like as a projection surface, such an illumination optical system has been devised that an enlarged image having a sufficient magnitude and a brightness on a projection surface can be obtained.
In a system using a plurality of image display elements, in particular, various types of illumination optical systems have been suggested to suppress degradation of the white color balance of color images or color shading thereof. As a light source for use in the illumination optical system of the projection type display apparatus disclosed, for example, in JP-A-10-171045, an ultra high voltage mercury lamp having a high luminous efficiency (70 lm/w) per unit input power is predominantly employed.
In order to increase transmissivity in a first or a second array lens, on the other hand, it is required to reduce a distance between electrodes as a big development issue. Since the ultra high voltage mercury lamp generates a large quantity of ultra violet ray, which applies a large stress to an organic material such as a liquid crystal light valve or a polarizing plate forming the illumination optical system so that this causes big issues of life reduction of the valve or the polarizing plate as well as generation of brightness reduction in a short period of time by devitrification caused by electrode wear or by a haze phenomenon of a luminous tube.
To avoid the above issues, many projection type display apparatuses using red, green or blue light emitting diodes or using a solid-state light emitting element such as organic electroluminescence elements has been proposed as a new light source. In JP-A-2004-341105, for example, there is suggested a light source device which includes a solid-state light source, a phosphor layer which converts ultra violet light emitted from the solid-state light source into visible light, and a transparent base material.
Further, in order to solve the problem in JP-A-2004-341105, there is suggested a light source device in which a solid-state light source can emit exciting light even as visible light at high efficiency, as shown, for example, in JP-A-2009-277516.
There is also suggested a light source device in a projection type display apparatus which includes a combination of light source units based on different light emission principles, for example, in JP-A-2009-259583.
In the technique disclosed in JP-A-2004-341105, there is shown a light source device which includes a solid-state light source, a phosphor layer for converting ultra violet light emitted from the solid-state light source into visible light, and a transparent base material. In this technique, since an exciting light source for using ultra violet light having a high energy as exciting light is employed, an optical component illuminated with the ultra violet light tends to be more damaged and thus it becomes difficult to secure the performance of the optical component throughout a long period of time. To avoid this, it is suggested to illuminate a phosphor layer with visible light having an energy lower than ultra violet light as an exciting light in JP-A-2009-277516.
Also as shown in JP-A-2009-259583, there is a new light source device in a projection type display apparatus which includes a combination of a plurality of types of light source units based on different light emitting principles. In this suggestion, the light source device includes a first light source unit as a light emitting diode or a solid-state light emitting element for emitting light having a predetermined wavelength, a second light source unit as a light emitting diode or a solid-state light emitting element for emitting exciting light, and a third light source unit for emitting light having the same wavelength range as the first light source unit as an exciting energy.